The scope of the project has expanded considerably because of the promising data from our recent studies relating the effects of metabolites on glycoprotein lateral mobility to their effects on cytoskeleton organization. Thus in addition to studying the mechanisms of cell shape control in erythrocytes, we plan to characterize the factors controlling glycoprotein lateral mobility and understand their mode of action. Our earlier studies indicate that an immobile fraction of band 3 (an integral membrane, glycoprotein, also the anion channel) is attached to the membrane skeleton or shell and that the mobile fraction of band 3 is sterically hindered in its lateral diffusion by the shell. Preliminary experiments indicate that the mobility of the mobile component is increased by metabolites such as 2,3 DPG (2,3 diphorphoglycerate) and the lipid, triphosphatidyl-inositol which dissociate the shell. The immobile as well as the mobile component appears to be mobilized by GTP. This project will examine other factors to determine the relative importance of metabolites in controlling glycoprotein lateral mobility. Biochemical studies of band 3 attachment to ankyrin and spectrin will explore the molecular basis of observed changes in the immobile fraction of band 3. Correlations of these findings will be made with deformability and band 3 rotational mobility studies performed on the same cells. In addition, a 3T3 cell line, which requires inositol for growth, will be examined to determine the effect of the phosphatidyl inositols on glycoprotein lateral mobility. These findings will increase our general understanding of cellular mechanisms of controlling glycoprotein-cytoskeletal interactions. The control of cell shape involves not only the cytoskeletal architecture but also the physical properties of the plasma membrane. The human erythrocyte provides the best system for studying membrane shape because it lacks cytoplasmic organelles and the extensive cytoskeleton of other cells. We have found that erythrocytes can sense changes in their shape caused by amphipathic drugs and can restore their shape to a biconcave disc form. This process seems to require energy and leaves an imbalance in the membranes which causes the opposite shape change when drugs are washed away. Several mechanisms are proposed to explain the restoration of shape along with experiemental tests of each. After defining the mechanism of shape restoration, studies are proposed to explore the sensing mechanism. This will provide a basis for further studies of cell membrane shape control and of sensory mechanisms in membranes.